Silence rate limit errors and raise job failures

Yammer rate limits 10 requests per 30 seconds. If a job gets rate limited then don't send that exception to Airbrake to reduce noise, since it will be retried. If after 5 tries, the job is still seing a rate limit, then `#failure` will notify us via Airbrake.

This will also notify us of any other job failures we experience.

https://trello.com/c/J5EBh49T